On land engines Mr. Sickels’ invention of the trip cut-off stimulated inventors to a multitude of devices for working steam expansively. Of these the one of enduring excellence proved to be that of Mr. Corliss. He applied the trip cut-off to the rotating slide valve, and arrested the motion of the liberated valve by an air-cushion. This proved a satisfactory method, as the valve, moving in directions parallel to its seat, did not need to be stopped at a determinate point. Mr. Corliss applied the governor to vary the point of liberation of the valve, and so produced a variable cut-off, which effected a large saving of steam and regulated the motion of the engine more closely than could be done by a throttle valve outside the steam-chest. This was by far the most prominent of the numerous forms of automatic variable cut-offs, to all of which it was supposed that the liberating feature was essential. In England, when the steam was worked expansively, it was cut off by a separately driven valve on the back of the main slide valve, the point of cut-off being fixed; and the regulation was effected by means of the throttle. This system was also largely employed in this country. The compound engine was unknown in the United States. I once saw at some place in New York City, now forgotten, a Wolff engine--a small beam-engine, which had been imported from England. It was visited as a curiosity by several engineers, and I remember Mr. Horatio Allen, then president of the Novelty Iron Works, remarking, “It is only a cut-off.” In the south of England the Wolff system was used to a limited extent. I was much interested in the McNaught system, devised, I think, by the same Scotchman who first applied a rotating paper drum to the Watt indicator. The cotton and woolen mills, as their business grew, felt the need of additional power, but dared not employ higher steam pressures in their cylinders, because the beam centers of their engines would not stand the additional stress. McNaught provided an additional cylinder to carry a higher pressure, and applied this pressure directly to the connecting-rod end of the beam. The exhaust from this cylinder was taken into the old cylinder at the old pressure. This latter cylinder then exerted the same power it always had done. The stresses on the beam centers were not increased, but the power of the engine was doubled, and only a little more steam was used than before. This method of compounding was known as McNaughting, and became common in the manufacturing districts of England and Scotland. There was one feature which was common to all engines in America and Europe, both ashore and afloat, and of whatever make or name, except locomotives. That was the piston speed, which varied only from 200 to 300 feet per minute. This last was the maximum speed, to which every new engine, however novel in other respects, was made to conform.